(1) Field of the Invention
The present invention relates to an anti-skid controlling system and method applicable to an automotive vehicle and, more particularly, relates to the anti-skid controlling system used for rear tire wheels which can achieve a shortening of a braking distance during a turning or cornering of the vehicle.
(2) Description of the Background Art
A Japanese Patent Application First Publication No. Showa 60-143169 (having a priority based on a German Patent Application No. P 83 21 370.4) published on Jul. 29, 1985 exemplifies an anti-skid control system in which a lateral acceleration is detected and a limitation of a braking liquid pressure is changed or released when a predetermined lateral acceleration is imposed on its vehicle body.
On the other hand, when a slip rate of a tire wheel of an automotive vehicle exceeds a set slip rate during a vehicle braking, a braking force of the vehicle (usually a braking pressure) is limited by means of an anti-skid actuator so as to prevent the tire wheel from being locked. The set slip rate is determined to be in the proximity to an ideal slip rate which provides a maximum frictional coefficient between the corresponding tire wheel and a road surface so that the vehicular braking distance gives a shortest distance.
Furthermore, when the anti-skid control for right and left rear tire wheels is carried out and the braking force difference is present due to the difference in the road surface frictional coefficient between the rear right and left tire wheels since the rear right and left tire wheels are not steered, the vehicle becomes spun. Hence, it is usual that the anti-skid control is carried out commonly to both rear right and left tire wheels on the basis of data on the slip rate from one of the rear tire wheels on which the slip rate is larger (i.e., its tire wheel is locked earlier).
In the case of the common anti-skid control for both right and left tire wheels described above, the braking forces on both rear tire wheels are mutually the same and their braking forces are referenced to one of the rear tire wheels at which the earlier lock occurs (easier to be locked).
Therefore, during the vehicular turning or cornering and the vehicular braking, a weight applied to an outer rear wheel is made heavier than that applied to an inner rear wheel so that the outer rear wheel is made difficult to be locked than the inner rear wheel. However, since the anti-skid control common to both rear inner and outer wheels is carried out, the braking force applied to the outer rear wheel is suppressed below a naturally generated value of braking force. Hence, the braking force for the whole vehicle is accordingly reduced and the braking distance becomes elongated.